Diabetes is one of lifestyle-related diseases with the background of change of eating habit and lack of exercise. Hence, diet and exercise therapies are performed in patients with diabetes. Furthermore, when its sufficient control and continuous performance are difficult, drug treatment is simultaneously performed. In addition, it has been confirmed by large-scale clinical trial that it is necessary to practice a long-term control of blood sugar level strictly so as to prevent patients with diabetes from occurring and advancing diabetic complications by receiving treatment (see the following References 1 and 2). Furthermore, many epidemiologic studies on impaired glucose tolerance and macroangiopathy show that impaired glucose tolerance as the boundary type is also a risk factor in macroangiopathy as well as diabetes. Thus, needs to improve postprandial hyperglycemia have been focused (see the following Reference 3).
In recent years, development of various antidiabetic agents has been progressing with the background of a rapid increase of patients with diabetes. For example, α-glucosidase inhibitors, which delay carbohydrate digestion and absorption at the small intestine, are used to improve postprandial hyperglycemia. It has been also reported that acarbose, one of α-glucosidase inhibitors, has an effect of preventing or delaying the incidence of diabetes by applying to patients with impaired glucose tolerance (see the following Reference 4). However, since α-glucosidase inhibitors do not affect elevated glucose levels by ingesting a monosaccharide of glucose (see the following Reference 5), with recently changing compositions of sugars in meals, it has been desired to develop agents which exert a wider range of activities inhibiting carbohydrate absorption.
In the meantime, it has been known that SGLT1, sodium-dependent glucose transporter 1, exists in the small intestine which controls carbohydrate absorption. It has been also reported that insufficiency of glucose and galactose absorption arises inpatients with dysfunction due to congenital abnormalities of human SGLT1 (see the following References 6-8). In addition, it has been confirmed that SGLT1 is involved in glucose and galactose absorption (see the following References 9 and 10).
Furthermore, it is confirmed that mRNA and protein of SGLT1 increase and absorption of glucoses are accelerated in OLETF rats and rats with streptozotocin-induced diabetic symptoms (see the following References 11 and 12). Generally in patients with diabetes, carbohydrate digestion and absorption are increased. For example, it is confirmed that mRNA and protein of SGLT1 are highly increased in the human small intestine (see the following Reference 13).
Therefore, blocking a human SGLT1 activity inhibits absorption of carbohydrates such as glucose at the small intestine, subsequently can prevent increase of blood sugar level. Especially, it is considered that delaying glucose absorption based on the above mentioned mechanism is effective to normalize postprandial hyperglycemia. In addition, since increase of SGLT1 in the small intestine is thought to contribute to increased carbohydrate absorption, fast development of agents, which have a potent inhibitory activity in human SGLT1, has been desired for the prevention or treatment of diabetes.    Reference 1: The Diabetes Control and Complications Trial Research Group, N. Engl. J. Med., 1993.9, Vol. 329, No. 14, pp. 977-986;    Reference 2: UK Prospective Diabetes Study Group, Lancet, 1998.9, Vol. 352, No. 9131, pp. 837-853;    Reference 3: Makoto, TOMINAGA, Endocrinology & Diabetology, 2001.11, Vol. 13, No. 5, pp. 534-542;    Reference 4: Jean-Louis Chiasson and 5 persons, Lancet, 2002.6, Vol. 359, No. 9323, pp. 2072-2077;    Reference 5: Hiroyuki, ODAKA and 3 persons, Journal of Japanese Society of Nutrition and Food Science, 1992, Vol. 45, No. 1, pp. 27-31;    Reference 6: Tadao, BABA and 1 person, Supplementary volume of Nippon Rinsho, Ryoikibetsu Shokogun, 1998, No. 19, pp. 552-554;    Reference 7: Michihiro, KASAHARA and 2 persons, Saishin Igaku, 1996.1, Vol. 51, No. 1, pp. 84-90;    Reference 8: Tomofusa, TSUCHIYA and 1 person, Nippon Rinsho, 1997.8, Vol. 55, No. 8, pp. 2131-2139;    Reference 9: Yoshikatsu, KANAI, Kidney and Dialysis, 1998.12, Vol. 45, extra edition, pp. 232-237;    Reference 10: E. Turk and 4 persons, Nature, 1991.3, Vol. 350, pp. 354-356;    Reference 11: Y. Fujita and 5 persons, Diabetologia, 1998, Vol. 41, pp. 1459-1466;    Reference 12: J. Dyer and 5 persons, Biochemical Society Transactions, 1997, Vol. 25, p. 479S;    Reference 13: J. Dyer and 4 persons, American Journal of Physiology, 2002.2, Vol. 282, No. 2, pp. G241-G248